Screw anchor

ABSTRACT

A screw anchor used in securing a guy wire to the ground includes at least one helical cutting blade attached to a generally square-shaped shaft, one end of which is pointed to facilitate the insertion of the screw anchor into the ground. Located near the other end of the shaft is a generally circular cross-sectional groove which forms an installation hub out of the other end of the shaft, and which is designed so that the torsional ultimate strength of the shaft at the groove is less than the torsional yield strength of the full square-shaped shaft. Extension rods are connectable to the end portion of the shaft forming the installation hub for increasing the length of and securing the guy wire to the screw anchor.

United States Patent Roza [4 1 May 16, 1972 54] SCREW ANCHOR 3,016,1171/1962 Petersen ..52/157 [72] Inventor: Kenneh Ralph Rom Chicago, L3,439,938 4/1969 Dunton ..287/108 [73] Assignee: Joslyn Mfg. and SupplyCo., Chicago, Ill. Primary Examiner-Donald Griffin Attorney-Mason,Kolehmainen, Rathbum & Wyss [22] Filed: Dec. 28, 1970 21 Appl. N6;101,624 1 ABSTRACT A screw anchor used in securing a guy wire to theground in- 52 us. (:1 ..24/11s B, 52/157, 287/108 dudes least helicalCutting blade mached 3 generally [51] Int. Cl ..E02d 5/74 square'shapedShaft Om end of which is Poimed to facilitate 58 Field ofSearch..24/279, 115 B; 52 165, 157; the the screw mated 287/108 near the otherend of the shaft is a generally circular cross-sectional groove whichforms an installation hub out of the other I 56] References Cited end ofthe shaft, and which is designed so that the torsional ultimate strengthof the shaft at the groove is less than the tor- I D STATES PATENTSsional yield strength of the full square-shaped shaft. Extension .rodsare connectable to the end portion of the shaft forming 505,81 1 10/1893Brown ..52/157 the installation hub f incl-easing the length f andcuring 1,193,725 8/1916 Smith ...52/157 the guy wire to the Screw anchor2,085,074 6/1937 Boyles ....287/108 2,864,633 12/1958 Mackie ..52/157 X6 Claims, 5 Drawing Figures PATENTEDHAY 16 I972 3, 662,436

AWE/W02 KENNETH A. Roz/4 777M022, (Me/Zmmm, fa/lMzz m, and 71944,

ATTOEA/E Y5 SCREW ANCHOR This invention relates to screw anchors and,more particularly, to a new and improved shaft structure for screwanchors.

Screw anchors are generally used to secure a guy wire and the like tothe ground. Commercially available screw anchors include a solid,generally square-shaped shaft to which is affixed at least one cuttingblade that enables the screw anchor to be inserted into the ground uponthe application of an installing torque on the shaft of the screwanchor. One end of the shaft is pointed to facilitate the insertion ofthe screw anchor into the ground, and the other end is adapted toreceive an extension rod so that the screw anchor can be increased toany desired length.

The installing torque exerted on the shaft of the screw anchor caneither be manually applied, or be applied by a power actuated wrench.During the installation of the screw anchor, both the pointed end of theshaft and the cutting blade affixed to the shaft encounter or strikevarious obstructions. As the torque is increased on the shaft due to theoccurrence of the obstructions, the shear stresses on the shaft and thecutting blade may be increased beyond the torsional yield strength ofthe square shaft. As a result, the screw anchor is rendered unusable asthe shaft tends to be weakened or shear apart under the increasedtorque. Furthermore, the removing of any portion of the screw anchoralready inserted into the ground can be quite difficult.

Accordingly, one object of the present invention is to provide a new andimproved screw anchor.

Another object is to provide a new and improved shaft structure for ascrew anchor to improve the usefulness of the screw anchor.

In accordance with these and many other objects, an embodiment of thepresent invention comprises a screw anchor for securing a guy wire orthe like to the ground having a generally square-shaped shaft to whichis affixed at least one cutting blade to enable insertion and retentionof the screw anchor in the ground. One end of the shaft is pointed tofacilitate the installation of the screw anchor into the ground and nearthe other end of the shaft is located a generally circularcross-sectional groove which forms an installation hub for the shaft.The groove is designed so that the torsional ultimate strength of theshaft at the groove is less than the torsional yield strength of thefull square-shaped shaft. An extension rod is connectable to theinstallation hub for increasing the screw anchor to any desired length.

Many other objects and advantages of the present invention will becomeapparent from considering the following detailed description inconjunction with the drawings in which:

FIG. I is a perspective view of the screw anchor embodying the presentinvention;

FIG. 2 is a side elevational view of a portion of the screw anchor shownin FIG. 1;

FIG. 3 is a cross-sectional view of the shaft portion of the screwanchor shown in FIG. 2 taken along line 33;

FIG. 4 is a perspective view of a portion of the screw anchor shown inFIG. 1 with an extension rod attached thereto; and

FIG. 5 is a perspective view of an extension rod connectable to thescrew anchor shown in FIG. 1.

Referring now more specifically to FIG. 1 of the drawings, therein isillustrated a screw anchor which is indicated generally as and whichembodies the present invention. The screw anchor 10 includes a generallysquare-shaped shaft 12, one end of which is formed into a point 14 thatfacilitates the insertion of the screw anchor 10 into the ground.Located near the other end of the shaft 12 is a generally circularcrosssectional necked down portion or groove 16 which forms aninstallation hub 18 out of the other end of the shaft 12. The groove 16is designed so that the torsional ultimate strength of the shaft 12 atthe groove 16 is less than the torsional yield strength of the fullsquare-shaped shaft 12 at any other position along the shaft 12.

A pair of cutting blades and 22 are welded or forged to the shaft 12between the groove 16 and the pointed end 14.

The generally helical shape of the cutting blades 20 and 22 enable theinsertion of the screw anchor into the ground upon the exertion of anappropriate installing torque to the shaft 12 at the installation hub18. The cutting blade 20 is positioned on the shaft 12 so that the blade20 follows or tracks the helical path cut by the cutting blade 22 duringthe installation of the screw anchor 10 into the ground. By so locatingthe blade 20 on the shaft 12, a multi-helix screw anchor 10 isinstallable into the ground with substantially the same installationtorque as is required for a screw anchor with only one cutting blade.

Many times during the advancement of the screw anchor 10 into theground, the cutting blades 20 and 22 and the pointed end 14 encounternumerous obstructions, or an angular movement occurs between the blades20 and 22 causing distortion of the tracking by the blade 20 of the pathcut by the blade 22. In order to overcome such obstructions ordistortions, the torque applied to the shaft 12 of the screw anchor 10may be increased to a value greater than the torsional ultimate strengthof the shaft 12 at the groove 16. As long as the installation torque isapplied to the installation hub 18, the shaft 12 shears apart upon theextraordinary increase in the installation torque only at the groove 16before the torque is increased to the torsional yield strength of thefull square-shaped shaft 12.

If it were not for the groove 16 being located near the end portion ofthe shaft 12, the installation torque might be increased above thetorsional yield strength of the full square shaft 12. The shaft 12 couldshear apart or be substantially weakened anywhere along its length sothat removal of any portion of the screw anchor 10 already in the groundcould be quite difficult or the ultimate holding strength of the anchor10 could be lessened. On the other hand, with the groove 16 located nearone end of the shaft 12, the shearing occurs only at the preferredlocation near the end of the shaft 12 so that once the installation hub18 is completely removed the screw anchor 10 can easily be removed fromthe ground or the installation of the screw anchor 10 can be continuedwithout any decrease in the holding strength of the anchor 10.

Accordingly, the groove 16 acts as a fail-safe mechanism which, atfailure, indicates that the torque being applied to the screw anchor 10is approaching the torsional yield strength of the shaft 12, that thehelical path for the blades 20 and 22 is being distorted, or that theoptimum depth for the screw anchor 10 has been reached. Of course, oncethe installation hub 18 is removed after a failure at the groove 16, thescrew anchor 10 can be further inserted into the ground by directlycoupling an installing device to the full square-shaped shaft 12, but inso doing, the torsional yield strength of the shaft 12 may be exceeded.

Once the screw anchor 10 has been inserted into the ground to a pointnear the groove 16, an extension rod 24, shown in FIG. 5 can be attachedto the end of the shaft 12 forming the installation hub 18. Theextension rod 24 has a generally square-shaped shank portion 26 throughone end of which is insertable a fastener 30 which secures a coupler 32to the extension rod 24. The coupler 32 has a pair of holes 34 and 36which correspond to a pair of holes 38 and 40 located on either side ofgroove 16 on the shaft 12. By inserting fasteners through the holes 34and 36 and the holes 40 and 38, respectively, the coupler 32 secures theextension rod 24 to the shaft 12 and overlaps the groove 16. With thecoupler 32 overlapping the groove 16, the shaft 12 has a uniformtorsional yield strength along its entire length.

To protect the shaft 12 and the shank portion 26 from shearing apartanywhere along their lengths due to possible excessive installationtorques, a generally circular cross-sectional groove 44 similar to thegroove 16 is located near the other end of the shank portion 26 so thatan installation hub 46 is formed out of the other end of the shankportion 26. Accordingly, as the insertion into the ground of the screwanchor 10 with the extension rod 24 attached to the shaft 12 iscontinued, any installation torque exerted on the installation hub 46above the torsional ultimate strength of the shank portion 26 at thegroove 44 causes the extension rod 24 to shear apart only at the groove44.

Once the screw anchor is inserted into the ground with as many extensionrods 24 as desired attached thereto, an extension rod 48 having aneyelet 50, to which a guy wire can be connected, is secured to theappropriate installation hub 46, or as shown in FIG. 4, to theinstallation hub 18, by a coupler 52. The coupler 52 overlaps the groove16 on the shaft 12 or, in the alternative, overlaps the groove 44 on theshank portion 26 of the extension rods 24. Thus, once the screw anchor10 is inserted into the ground to the desired depth, the torsional yieldstrength of the screw anchor 10 is equivalent to the torsional yieldstrength of the full square-shaped shaft 12 or the shank portion 26 forthe couplers 32 and 52 overlap any of the grooves 16 or 44 that arepositioned along the shaft 12 or any of the shank portions 26.

Although the present invention has been described by reference to only asingle embodiment thereof, it will be apparent that numerous othermodifications and embodiments may be devised by those skilled in theart, and it is intended by the appended claims to cover allmodifications and embodiments which will fall within the true spirit andscope of the present invention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. A screw anchor installable into the ground by the application oftorsional forces so as to secure a guy wire or the like to the ground,said screw anchor comprising:

a shaft having a first necked down groove near one end to form aninstallation hub to which are applied said torsional forces,

at least one cutting blade attached to said shaft at a point spaced fromsaid first necked down groove,

an extension rod having a second necked down groove near a first endportion,

and a coupler means attachable to said extension rod at a second endportion and to said shaft at said installation hub, said coupler meansoverlapping said first necked down groove when attached to said shaft.

2. The screw anchor as set forth in claim 1 wherein the first neckeddown groove has a torsional ultimate strength less than the torsionalyield strength of the shaft.

3. Thescrew anchor as set forth in claim I wherein said shaft isgenerally square-shaped.

4. The screw anchor as set forth in claim 1 wherein said first neckeddown groove has a generally round cross section.

5. The screw anchor as set forth in claim 1 wherein said cutting bladeis welded to said shaft.

6. The screw anchor as set forth in claim 1 including first and secondhelical cutting blades attached to said shaft, said first cutting bladefollowing the path cut by said second cutting blade.

1. A screw anchor installable into the ground by the application oftorsional forces so as to secure a guy wire or the like to the ground,said screw anchor comprising: a shaft having a first necked down groovenear one end to form an installation hub to which are applied saidtorsional forces, at least one cutting blade attached to said shaft at apoint spaced from said first necked down groove, an extension rod havinga second necked down groove near a first end portion, and a couplermeans attachable to said extension rod at a second end portion and tosaid shaft at said installation hub, said coupler means overlapping saidfirst necked down groove when attached to said shaft.
 2. The screwanchor as set forth in claim 1 wherein the first necked down groove hasa torsional ultimaTe strength less than the torsional yield strength ofthe shaft.
 3. The screw anchor as set forth in claim 1 wherein saidshaft is generally square-shaped.
 4. The screw anchor as set forth inclaim 1 wherein said first necked down groove has a generally roundcross section.
 5. The screw anchor as set forth in claim 1 wherein saidcutting blade is welded to said shaft.
 6. The screw anchor as set forthin claim 1 including first and second helical cutting blades attached tosaid shaft, said first cutting blade following the path cut by saidsecond cutting blade.